const int LED[] = {11, 10, 9, 8, 7, 6, 5, 4};

void setup() {
  for (int i = 0; i < 9; i++) {
    pinMode(LED[i], OUTPUT);
    digitalWrite(LED[i], HIGH);
  }
}

void loop() {
  for (int i = 0; i < 3; i++) {
    digitalWrite(LED[3-i], LOW);
    digitalWrite(LED[4+i], LOW);
    delay(100);
    digitalWrite(LED[3-i], HIGH);
    digitalWrite(LED[4+i], HIGH);
  }
  for (int i = 0; i < 3; i++) {
    digitalWrite(LED[i], LOW);
    digitalWrite(LED[7-i], LOW);
    delay(100);
    digitalWrite(LED[i], HIGH);
    digitalWrite(LED[7-i], HIGH);
  }
}